In modern commercial vehicle, pneumatic systems such as compressed air brakes are frequently used. Compressed air supply devices, which in the meantime frequently have an electronic control device, serve for supplying such pneumatic systems with compressed air. In order to be able to actuate valves of the compressed air supply device via the electronic control device in a specific manner, the valves are frequently designed as solenoid valves. Therefore, a precise controlling of compressed air which is provided via a compressor and a regeneration of the air filter can be achieved.
In order to safeguard the compressed air supply for such important systems such as brakes in the event of failure of the electronic control device, for example as a result of a faulty power supply or on account of a sensor failure, provision is usually made for a back-up level which functions even without an electronic control device. However, the possibility of directed actuation of the valves is then also omitted. For example, the compressor as a rule can no longer readily be put into an energy saving state if an operating pressure of the compressed air supply device is achieved. This can lead to the compressor continuing to operate against a high pressure over a long period until a relief valve blows off the pressure at a maximum pressure level. This can lead to a considerable loading of the compressor which, for example, can even damage the compressor as a result of overheating. Furthermore, a regeneration, which can no longer be carried out, leads to air filters and consumer systems, such as brakes, being operated in a wet state.
It is an object of the present invention, in the case of an electronically controlled compressed air supply device, to provide a back-up level which enables an improved control of the compressed air supply device, and especially of a compressor, in a purely pneumatic way.
According to the invention, provision is made for a compressed air supply device for commercial vehicles which is electrically connected, or electrically connectable, to an electronic control device. The compressed air supply device has at least one control valve which can be controlled via the electronic control device, wherein the control valve has at least one inlet port, a vent port and an outlet port. A control line is connected to the outlet port of the control valve, wherein the control line is connected, or connectable, to a control input of a compressor and/or to an air filter for a regeneration. Provision is made for a supply line via which compressed air is directed, or can be directed, to an inlet port of the control valve, and also a vent line which is connected to the vent port of the control valve. Furthermore, provision is made for back-up valve, wherein an inlet of the back-up valve is connected to the supply line and an outlet of the back-up valve is connected, or connectable, to the vent line. The back-up valve is designed in such a way that it opens pneumatically if there is a pressure in the supply line which corresponds to a predetermined opening pressure, or exceeds this. Therefore, via the back-up valve provision can be made for a pneumatic back-up level which even with a failed electronic control device enables a pressure build up in the control line via the back-up valve—which is switched into the open position—the vent line and the vent port of the control valve. Therefore, via the control line a compressor, for example, can be controlled in such a way that it is switched into an energy-saving state.
Alternatively or additionally, the carrying out of a regeneration is possible without a functioning electronic control device. The back-up valve can have a vent outlet close to its inlet and its outlet, which can be connected, or be connectable, to a vent to atmosphere.
Pneumatic opening of the back-up valve means that the back-up valve pneumatically creates a fluid-conducting connection between its inlet and its outlet. In this case, a possibly existing vent outlet of the back-up valve can be shut off. Pneumatic closing of the back-up valve means that the back-up valve shuts off or breaks a connection between the outlet of the back-up valve and the inlet of the back-up valve. In this case, a connection between the outlet and a possibly existing vent outlet of the back-up valve can be created.
The back-up valve can have a normal position and an open position. The normal position can correspond to the position which the back-up valve occupies if the pressure in the supply line is insufficient for the opening of the back-up valve. In the normal position, the connection between an inlet and an outlet of the back-up valve can be shut off. Should the back-up valve have a vent port, a connection between the outlet of the back-up valve and the vent outlet can be provided in the normal position. In the open position, the inlet of the back-up valve can be connected to the outlet of the back-up valve. A possibly existing vent outlet of the back-up valve can be shut off.
The back-up valve can be designed in such a way that as a result of a pneumatic opening it occupies the open position, that is to say transfers from the normal position into the open position when the opening pressure in the supply line is achieved or exceeded. The back-up valve can be a 3/2 directional valve. As a result, leakages of the back-up valve, which lead to compressed air being able to flow from the supply line to the outlet of the back-up valve in the normal state, can especially be compensated. The 3/2 directional valve can especially have an inlet, an outlet and a vent outlet. In the normal position, the outlet can preferably be connected to the vent outlet of the 3/2 directional valve.
Alternatively, the back-up valve can be a 2/2 directional valve. As a result, a particularly simple and inexpensive construction can be achieved.
The actuation of the control valve can be electrically carried out by the electronic control device in an indirect or direct manner, for example by energizing electromagnetic components of the valve. The control valve can especially be designed as a solenoid valve. It is also conceivable that the control valve, in addition to a pneumatic valve, has a solenoid valve component for piloting the pneumatic valve, which is actuated by the electronic control device. It is conceivable to design the control valve as a 3/2 directional valve. The vent port of the control valve can be connected, or be connectable, via the vent line to a vent to atmosphere. In a normal position, the control valve can be switched in such a way that it connects the control line to the supply line, that is to say that a fluid-conducting connection exists between the outlet port and the vent port. The inlet port and therefore the supply line can be shut off in the normal position. Therefore, in the normal position of the control valve the control line can be vented, or be ventable. In a free-passage position of the control valve, the control valve can be switched in such a way that it connects the control line in a fluid-conducting manner to the supply line and shuts off the vent line. Therefore, the inlet port and the outlet port are interconnected in a fluid-conducting manner and the vent port is shut off.
The electronic control device can make it possible to switch the control valve between the normal position and the free-passage position. It can be expedient to design the control valve in such a way that it occupies the normal position if it is not actuated via the electronic control device and/or is not energized. To this end, provision can be made, for example, for a return device, such as a spring arrangement, which preloads the control valve in the normal position.
The electronic control device can be considered to be part of the compressed air supply device or can be formed separately therefrom. The compressed air supply device can comprise a compressor, or can be considered to be separate from the compressor or considered to be a separable device.
The control line can especially be connected, or be connectable, to a compressor control input, via which the compressor can be pneumatically controlled. It is conceivable, for example, that the compressor, when a pressure is applied to its control input, for example switches into an energy-saving mode via the control line. In an energy-saving mode, the compressor can, for example, be decoupled or disconnected from a drive or a shaft, or its output capacity can be greatly reduced. If no pressure is applied to the control input of the compressor, the compressor can be operated in such a way that it delivers compressed air for the compressed air supply device.
An air filter can be part of the compressed air supply system. A regeneration of the air filter can be carried out in such a way that compressed air from the compressed air supply device is blown off through the air filter to a vent to atmosphere in order to remove water and contaminants which have collected in the air filter. In this case, the control line can be connected, for example, to a check valve for the regeneration, or can be connected to an additional control valve which can act for controlling or initiating a regeneration.
Within the context of this description, a connection or fluid-conducting connection between two pneumatic components or a line and a pneumatic component such as a valve, constitutes a pneumatic connection via which compressed air can be directed. A commercial vehicle can especially be a lorry or a mobile working machine, such as a tractor. A rail vehicle can also be considered to be a commercial vehicle.
By means of the electronic control device, a normal operating pressure of the compressed air supply device can be predetermined and/or monitored. For example, the electronic control device can be designed in such a way to stop the compressed air feed when the operating pressure is achieved by, for example, the compressor being switched into its energy-saving mode. It can be provided that the electronic control device detects the pressure in the compressed air supply device at one point, or at a plurality of points, by means of suitable sensors, and shuts down or decouples the compressor when the desired operating pressure is achieved. To this end, the electronic control device can, for example, actuate the control valve in such a way that the control line is pressurized in order to apply a pressure signal to the compressor control input. An operating pressure can lie, for example, at about 12 or 12.5 bar. The operating pressure can especially be measured in the supply line.
For the protection of the compressed air supply device, provision is frequently made for a maximum safety pressure which the device must not exceed in any event. In order to avoid this safety pressure being exceeded, use is frequently made of a relief valve which undertakes a venting to atmosphere when said safety pressure is exceeded. The relief valve which is used for this can also be used as an actuated bleed valve for a regeneration, which opens a connection to atmosphere. The opening pressure of the back-up valve expediently lies below this safety pressure. It is also conceivable that the conventional relief valve is replaced by the back-up valve because by using the back-up valve an exceeding of the opening pressure in the compressed air supply device can be reliably prevented by shutting down the compressor and/or by initiating a regeneration or other bleed of pressure. Therefore, the opening pressure can be considered to be the safety pressure, for example.
It can be provided that the compressed air supply device also has at least one vent valve with an inlet, an outlet and an air bleed. The inlet of the vent valve is connected, or connectable, to the outlet of the back-up valve and the outlet of the vent valve is connected, or connectable, to the vent port of the control valve. Via the vent valve, switching between an aerating and venting of the vent port of the control valve can be quickly carried out. It is conceivable that more than one control valve is connected in each case via its vent port to the outlet of the vent valve and/or that at least one vent valve is associated with each control valve. The outlet of the vent valve can be connected, or be connectable, via the vent line to the vent port or to the vent ports of the control valves. Therefore, a connection between the back-up valve and the vent port of the control valve via the vent valve can be achieved. In general, a valve which has an inlet, an outlet and an air bleed can be considered to be a vent valve. The air bleed can be connected, or be connectable, to a vent to atmosphere. A vent valve can be designed as a 3/2 directional valve. It can be expedient that in the vent valve, when the inlet is vented, the outlet is connected to the air bleed and so is also vented. If the inlet is aerated, the vent valve can connect the outlet to the inlet and shut off the air bleed so that a fluid-conducting connection exists between inlet and outlet of the vent valve. In this position, the vent valve can be referred to as being open. Since a pressure is present at the aerated inlet, a line which is connected to the outlet is therefore aerated. A vent valve can especially be pneumatically actuated, or able to be pneumatically actuated.
The compressed air supply device can have a second control valve which can be actuated via the electronic control device, wherein an outlet port of the second control valve is connected, or connectable, to the air filter for a regeneration. The other control valve can be connected, or be connectable, via the control line to a control input of the compressor. As a result, especially with a suitable switched position of the second control valve, an air flow, which is provided for the regeneration of the air filter, can be directed via the outlet port of the second control valve. A regeneration line, which is provided for the regeneration of the air filter and which is connected to the outlet port of the second control valve, can therefore be considered to be a second control line which is associated with the second control valve. The second control valve can be designed similarly to the control valve described above and can especially have an inlet port, an outlet port and a vent port. The second control valve can be designed as a 3/2 directional valve. The second control valve can be a solenoid valve. A vent port of the second control valve can be connected to an associated second vent line. This second vent line can be connected, or be connectable, to a vent to atmosphere. It is conceivable that the second vent line is connected, or connectable, to the outlet of the back-up valve. Such a connection can be effected for example via an interposed valve. The interposed valve can be the aforementioned vent valve. In general, the outlet of the back-up valve can be connected, or be connectable, via a vent valve to the vent outlet of the first control valve and/or to the vent outlet of the second control valve. Provision can be made for a connection junction, for example, which connects the vent line which is connected to the control valve to the second vent line which is connected to the second control valve, and leads both to the vent valve.
In one development, a vent port of the second control valve can be connected to an outlet of a second vent valve, for example via an associated second vent line. Via the second vent valve, a fast and controlled venting of the second control valve can therefore be carried out.
It is conceivable that the outlet of the back-up valve is connected to the inlet of a second vent valve. Via the second vent valve, for example the actuation or compressed air supply of a second control valve is possible. Therefore, the back-up valve can also supply a second control valve with compressed air via the second vent valve in such a way that the outlet port of the control valve, with the back-up valve open, is pressurized, as a result of which for example a regeneration of the compressed air supply system independently of the electronic control device becomes possible.
Between the outlet of the back-up valve and the inlet of the at least one vent valve, provision can be made for a bypass line which is connected to a vent. Therefore, an undesirable pressure build-up upstream of the inlet of the vent valve can be prevented. The inlet of the vent valve can especially be connected via the bypass line to a vent to atmosphere. If more than one vent valve is provided, the bypass line can be arranged in such a way that it is connected to the inlets of all the vent valves. If no separate vent valve is provided, the outlet of the back-up valve can still be connected via a corresponding bypass line to a vent to atmosphere. Therefore, for example an undesirable pressure build-up in a vent line to a control valve can be avoided.
In one development, a restrictor can be provided in the bypass line. As a result, on the one hand an undesirable pressure build-up as a result of leakage in the back-up valve, for example, can be prevented, and on the other hand a desirable pressure build-up upstream of a vent valve or in a vent line can be carried out. The restrictor can especially have an effective flow cross section for a flow for venting to atmosphere which is smaller than an effective flow cross section for a flow from the outlet of the back-up valve to an inlet of the vent valve or to the inlets of the vent valves, or via a vent line to the vent port, or vent ports, of the vent valves, or via a vent line to the vent port, or ports, of at least one control valve. Therefore, a sufficient pressure build-up in the line to the inlet of the vent valve can be achieved, for example, so that the vent valve, or vent valves, with the back-up valve open, actually open themselves and a fluid-conducting connection between the inlets and outlets of these valves is created, although air discharges via the bypass line.
The at least one vent valve can be a fast-acting vent valve. Therefore, a particularly fast venting via the vent valve can be ensured. A fast-acting vent valve can especially provide a large flow cross section for a connection from its outlet to an air bleed for venting to atmosphere. A fast-acting vent valve can especially have a membrane which enables a fast switching over of the switching states of said fast-acting vent valve. Naturally, all the vent valves, which are connected to the back-up valve, can be designed as fast-acting vent valves.
It can be expedient that the opening pressure of the back-up valve is greater than an operating pressure which can be established, or is established, by means of the electronic control device. Via the back-up valve, therefore, for when the compressor delivery is over and above the predetermined operating pressure, the compressor can be shut down when the opening pressure is reached and be protected against overheating and/or a regeneration can be carried out.
The back-up valve can be designed in such a way that it closes pneumatically if the pressure in the supply line has dropped to a pressure below a predetermined closing pressure. The closing pressure can be equal to, or lower than, the opening pressure. It can especially be provided that the closing pressure is lower than the operating pressure so that a pressure range is defined in which the back-up valve is opened so as not to frequently switch the compressor back and forth between its switching states, for example, or in order to enable a complete regeneration of the air filter. A pneumatic closure on account of a lowered pressure can follow an opening of the back-up valve.